Chemical formula: KAl(SO4)2.12H2O
Synonyms: potassium aluminium sulphate dodecahydrate, potassium alum, aluminium sulphate (misnomer).
Amount: 200 g
Appearance and odour: mixture of small and larger white crystals, without appreciable odour
Packaging: professional wide necked, white HDPE bottle with blue conical seal cap and tamper evidence ring. Labelled. Bottle and cap are UN approved and reusable.
Description and uses: a double salt of aluminium sulphate and potassium sulphate used as a dye mordant and water treatment agent (flocculant) it is a primary source of soluble aluminium salt. Well soluble in cold water and highly soluble in hot water it is an ideal substance for crystal growing. It forms regular octahedral crystals with flattened corners and can be grown into very larger crystals with some patience. Mixed crystals with chromium alum or ferric alum can also be grown.
Add ammonia solution to an alum solution and hydrated aluminium hydroxide precipitates: the basis of most other aluminium salts. Add strong alkali (NaOH or KOH) to the precipitate and it dissolves to aluminate, a phenomenon known as amphoterism.